Candidate gene analysis of the IL12B gene in Crohn's disease

IL12B是克隆病(CD)易感基因的候选基因之一。本研究的目的是对日本人CD中IL12B的候选基因进行分析，并确定该危险等位基因对CD易感性的影响。因此，IL-12b基因在外周血单核细胞中的表达失衡。共检查了364名CD患者、242名溃疡性结肠炎(UC)患者和445名健康对照(HCS)。对IL12B附近的8个SNPs进行了基因分型。用快照分析法检测单核细胞中IL12B-mRNA的等位基因比例。2个SNP(rs6887695、rs41292470)与Cd显著相关(Pc分别为0.012、0.020)，1个SNP(Rs3212227)与Cd呈边际相关(Pc=0.1)。这3个SNP形成的单倍型A与CD显著相关(Pc=0.00054，优势比=1.46)。在10例单倍型杂合子的健康对照单核细胞中，单倍型A和非危险单倍型(单倍型B)转录的IL12B-mR NA的等位基因比率显著高于各自基因组DNA的等位基因比率(p=0.00069)。我们证实了IL12B单倍型1与日本CD的关联。已证实的等位基因表达失衡支持了IL12B的风险单倍型通过增加IL12B-mRNA的表达而增加CD易感性的观点。

IL12B is one of the promising candidates for susceptibility genes to Crohn's disease (CD). The aim of this study was to do a candidate gene analysis of IL12B in Japanese CD, and to determine how the risk allele affects the susceptibility to CD. Therefore, allelic expression imbalance of IL-12B mRNA was determined in peripheral monocytes. A total of 364 patients with CD, 242 patients with ulcerative colitis (UC) and445 healthy controls (HCs) were examined. Eight SNPs around IL12B were genotyped. The allelic ratio of IL12B-mRNA was examined using SNaPshot analysis in LPS-stimulated monocytes. Two SNPs (rs6887695, rs41292470) were significantly associated with CD (Pc = 0.012, 0.020, respectively) and one SNP (rs3212227) showed an association with marginal significance (Pc = 0.10). Haplotype A formed by these three SNPs showed significant association with CD (Pc = 0.00054, odds ratio = 1.46). The allelic ratios of IL12B-mRNA transcribed from the haplotype A to the non-risk haplotype (haplotype B) in LPS-stimulated monocytes from ten healthy controls heterozygous for the risk haplotype were significantly higher than the allelic ratio of respective genomic DNA (p= 0.00069). We confirmed the association of the haplotype 1 of IL12B with Japanese CD. The demonstrated allelic expression imbalance supports the idea that the risk haplotype of IL12B confers susceptibility to CD through increasing expression of IL12B-mRNA.